Semiconductor lasers are attractive for a wide variety of applications including telecommunications, computing systems, optical recording systems and optical interconnection of integrated circuits. Semiconductor lasers provide a compact source of coherent, monochromatic light which can be modulated at high bit rates to transmit large amounts of information.
Vertical cavity surface emitting lasers (VCSELs) are particularly promising for applications requiring two dimensional arrays of lasers. As contrasted with edge emitting lasers which emit light parallel to the growth planes of their substrates, VCSELs emit light perpendicular to the substrates. A typical VCSEL comprises an active region sandwiched between a pair of distributed Bragg reflector stacks. Upon injection of suitable current through the active region, laser light is emitted transverse to the planes of growth.
One difficulty with conventional VCSELs is the problem of confining emitted light laterally in the region of the laser cavity. Because the devices are grown as planar regions extending laterally beyond the intended active area, the regions laterally peripheral to the active areas have indices of refraction identical or very nearly equal to the indices of refraction in the active area. This matching permits lateral coupling away from the active area. Accordingly, there is a need for a VCSEL device providing enhanced optical confinement.